


Let Me Break You In

by halcyon1993



Series: The Kinky Adventures of a Wolf and His Boy [16]
Category: Teen Wolf (TV)
Genre: Age Difference, Anal Fingering, Anal Sex, Armpit Kink, Body Hair, Body Worship, Bottom Derek Hale, Cock Worship, Confident Stiles Stilinski, Daddy Kink, Father/Son Incest, First Time Bottoming, Foreskin Play, Gentle Sex, Human Derek Hale, Incest, M/M, Older Derek Hale, Oral Sex, Plot What Plot/Porn Without Plot, Post-Coital Cuddling, Praise Kink, Rimming, Top Stiles Stilinski
Language: English
Status: Completed
Published: 2018-06-08
Updated: 2018-06-08
Packaged: 2019-05-19 20:15:58
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 7,664
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14880494
Author URL: https://archiveofourown.org/users/halcyon1993/pseuds/halcyon1993
Summary: After his wife leaves him, Derek comes to realise that he isn't as straight as he'd always thought. When his son returns from college and he comes out to him, Stiles, an experienced top, offers to help him explore his new sexuality.





	Let Me Break You In

**Author's Note:**

  * For [Mulder200](https://archiveofourown.org/users/Mulder200/gifts).



> As always with this series, don't judge me for the depravity I have written...
> 
> If any of the subject matter present in this fic grosses you out, don't read it. Any comments that aren't constructive criticism will be deleted. Everyone else, enjoy! :D

You never stop learning new things about yourself, even when you're through your formative years and well into adulthood. Derek's mother used to tell him that when he was young. For most of his life, Derek believed there was nothing new to discover about his sexuality. He was attracted to girls and then to women, and he got married and had a kid and that was all he knew—or maybe all he cared to know. It was what all the other guys his age were doing, so he never questioned it, never stopped to consider that there might be more to it.

Then the mother of his child ran off and left him to raise their son, Stiles, by himself. He was deeply hurt at first, but he quickly got over it. Theirs was a shotgun wedding, rushed and not at all romantic because he accidentally got Paige pregnant when they were eighteen years old and they were both pressured into 'doing the right thing'.

They were never happy together, both of them feeling trapped even though neither admitted it. They pretended for a while, mostly for Stiles' sake, but when he looks back on it now, Derek supposes that it was only a matter of time until one of them had enough and ended things. He just never thought Paige would leave Stiles behind as well.

Struggling to accommodate the new hole in their lives, Derek and Stiles got even closer. They became best friends as well as father and son. They both knew they could tell each other anything without fear of being judged, even the most tightly held secrets, and after several long months Derek came to realise and take comfort from the idea that, if Paige could so easily abandon her son, both of them were better off without her in their lives.

Paige's departure also opened up a world of possibilities for Derek, which he hesitantly began to explore with Stiles' gentle nudging. He dated again but never found a woman he could see himself bringing home to introduce to his son. It was only after the one adult friend Derek had left suggested he try fishing in a different sea that Derek started to see the reason none of the women ever seemed right.

Maybe it was the real reason he and Paige never worked out, too.

Now, the day after Stiles moved back in after graduating from college, Derek paces back and forth in their living room, waiting for the twenty-two-year-old to get home. "Why the hell are you so nervous?" he asks himself, reflexively clenching and unclenching his hands at his sides. "Stiles told you he was bisexual years ago. It's gonna be fine. This won't change anything."

"What won't change anything?"

Startling violently, Derek spins around so quickly that he loses his balance and almost falls on top of their glass coffee table. He hadn't heard Stiles come home, but there he stands in the entrance to the living room, eyeing him with concern and alarm.

"You okay? You look pale," Stiles notes, stepping closer and putting a steadying hand on Derek's arm.

"Yeah, I'm fine," Derek replies, getting over his surprise. "Sit down, son. I have something I need to tell you."

"Sounds serious."

"It is."

Stiles chooses one end of the sofa, so Derek sits at the other. "What's this about, dad? You're kinda freaking me out."

"I've been doing some…soul-searching lately," Derek begins, twisting his hands nervously in his lap, "and I've come to realise something about myself that I want you to know about."

Stiles still looks concerned, but he visibly braces himself, his face calm and ready for anything. "Alright. Lay it on me."

The two words are difficult to get out, but then his son reaches over and puts a hand over both of his, stopping his fidgeting and giving him the confidence he needs.

"I'm gay."

Stiles has no immediate reaction. His face remains stolid, like he is waiting for something else or perhaps even the punchline to a joke. When Derek doesn't give him anything else, just sits and watches him anxiously, he seems to realise that those two words were all his dad had wanted to tell him and his countenance becomes soft and understanding.

"I'm glad you told me, but I already suspected something like that," he says, smiling.

Derek's eyebrows shoot up his forehead. "Y-you did?"

Stiles laughs good-naturedly. "I've seen you checking out other guys before, dude. You were pretty obvious."

His cheeks colouring, Derek bows his head. "Oh."

"Was that all you were getting yourself worked up about?"

"Yeah, that was all."

"Hey, it's no big deal. So you like dick. I happen to like dick, too. No big."

"That's a relief. I knew I was getting worked up for nothing, but I couldn't help it, y'know?"

Stiles nods. "I know. I was the same way when I came out to you."

"I remember."

"So…" Stiles rearranges himself into a more casual position, his legs folded under himself. "Have you done anything yet?"

"What?"

"Y'know, have you had sex with another guy yet?"

Derek blinks a few times and shakes his head, suddenly embarrassed. "Have you?" he counters.

"Of course. Lots of times. I've been told I'm very good at using what my dad gave me." Stiles winks.

Stiles has always been free when discussing his sex life—he told his dad right after he lost his virginity five years ago—so Derek isn't made uncomfortable discussing this. The fact that Stiles is keeping it light helps tremendously, because what they are talking about this time is uncharted territory for him.

"Top or bottom?" Stiles asks him, grinning mischievously.

"Uh…I dunno. I haven't done anything yet, remember?"

Stiles waves a dismissive hand. "That doesn't mean anything. Even when you were with mom you could've been the one getting fucked most of the time for all I know. So: top or bottom?"

"I've never— I've only ever been the one doing the, y'know…the fucking."

"Are you curious?"

"Yes," Derek answers honestly, his asshole clenching.

"Well, I'm exclusively a top myself," Stiles reveals, unashamed as ever. "I tried bottoming a few times, but it just wasn't for me. It felt good, don't get me wrong, but I just prefer to be on the other side of things."

"I see."

Stiles eyes him strangely for a few moments, his expression inscrutable, and then it changes to what Derek thinks of as his Idea Face—the one he gets whenever he thinks of some great scheme he can't wait to carry out. Derek prepares himself, because when his son wears that expression, they are usually both in for what can kindly be described as an interesting ride. Sure enough, when Stiles tells him what he has just thought of, Derek gapes, because it's so ridiculous that he struggles to comprehend it.

"What if you bottom for me?" Stiles suggests happily, apparently not seeing a problem with it.

Still gaping like a fish, Derek fumbles for a reply. "Son, that's…we can't do that."

"Why not?"

"I'm your dad, for one thing! It's wrong."

Stiles shrugs, not bothered at all. "Only if someone else knows about it."

"We're definitely not doing that."

Not giving up so easily, Stiles shuffles sideways on the sofa until their thighs touch and leans in so that their faces are close together. "C'mon, let me do this for you."

Derek says nothing. He doesn't think he could, even if he could think of the right words.

"Like I said, I've got a nice dick and know how to use it. I'll make it good for you."

Remaining silent, Derek raises his hands to push Stiles away when the younger man closes the distance between them and starts kissing a path across his scratchy jaw, but when he puts his hands on his son's shoulders he doesn't follow through, just rests them there. Stiles keeps going, starting with the side of Derek's face and then finally reaching his mouth. When their lips connect, Derek gasps out of shock, which gives his son the perfect opportunity to slide his tongue inside of his open mouth. He doesn't reciprocate right away, but Stiles manages to coax him into it and he kisses his son tentatively back.

He should feel grossed out—this is his baby boy; it's immoral, disgusting—but his body betrays him, his cock getting hard in his jeans.

"Stiles," he whispers against his lips.

"Let's take this to your bedroom," Stiles whispers back.

He takes Derek's hands from his shoulders, drops one of them and pulls him up from the sofa with the other. Derek walks docilely behind him, still too stunned to do anything else.

When they reach the master bedroom and his son closes the door behind them, Derek knows he has to stop this now. "Stiles—"

"Ah-ah-ah," the boy chides softly, putting his index finger to his dad's lips. "It's all gonna be okay."

The next thing Derek knows, Stiles tugs at the hem of his red henley and rucks it up to his armpits. He is still unsure if he should be letting him do this, but he finds himself raising his arms so that Stiles can take his shirt off all the way. When it's on the floor, his son kisses him again, soft hands running over every inch of his hirsute chest, exploring.

Derek moans into Stiles' mouth when he reaches his nipples and twists them, a kink Derek didn't know he had now being revealed to him. The moan and how he thrusts his chest out must be clear enough signs for Stiles to figure out how much he likes having his nipples played with, because the younger man starts twisting and pinching both of them between his thumbs and index fingers, the pain and pleasure of it shooting right to Derek's aching cock.

Once his nipples are both sore and red, Stiles releases them and walks him backward. Derek's knees hit the foot of his bed and then his son pushes him so that he falls back onto it.

Things are moving so quickly, but Derek is now too swept up in everything Stiles is doing to him to even think of acting like a father should and putting an end to the proceedings. His mind is clouded with lust, lowering his inhibitions and getting rid of any qualms he had altogether. He never thought it would feel so good to have someone else calling the shots. In the rare instances that he and his ex-wife had sex after they were pressured into getting married and Stiles was born, Derek was always the one taking charge and it was never very exciting—just boring missionary, again and again, with neither of them really being into it.

That isn't the case here, though.

No, the wrongness of what he and Stiles are doing does a very good job of making things exciting, a feeling that Derek has sorely missed. He realises as Stiles begins to undo his jeans that he doesn't want to stop anymore, even if he could gather himself together enough to do so. He gives in.

"Stiles…" he breathes, readily lifting his hips off of the bed so that his son can strip him entirely.

Bared to him now, the younger man pauses for a moment to take in the sight of him. Derek wonders if he likes what he sees.

"Look at you," Stiles says reverently, giving him his answer. "So fucking hot. I always knew it."

"You did?"

His son meets his eyes. "Yeah. I've liked looking at you since I was ten. I jerked off for the first time after I caught a glimpse of you in the shower one afternoon."

Derek is stunned. He never would have guessed. He listens raptly as his son continues to speak.

"That was one hell of a sexual awakening, let me tell you." Stiles chuckles, kneeling on the carpeted floor and putting his hands on Derek's knees. "Seeing you there, all wet and soapy…God, the things it did to me. You didn't notice me. You had your front to me at first, and when I got bigger I realised that you were where I got my cock from. It was a bit distorted because of the glass, but even when soft, you were big. And then you turned around to wash the shampoo out of your hair and I saw your ass and nearly came in my pants right there in the doorway. I never went after you because I didn't wanna spook you, but I'm tired of waiting and this was too perfect an opportunity to pass up."

Derek takes a breath and then nods jerkily, finally ready to accept his son's offer. "Do it."

With a smile, Stiles kisses the inside of Derek's knee. "Yeah?"

"Yeah. I want you."

"Where? Tell me… _daddy_."

Stiles hasn't called him that in years, since he got too old and it changed to just 'dad'. Back then it was never said like this, Stiles' lips curling around the word, making it drip with sex. Derek finds himself surprisingly turned on by it.

"I want you inside me," he responds breathily.

* * *

Those five words are like music to Stiles' ears.

Like he just told his dad, he has been anticipating this day for years, never knowing whether it would actually come to pass. Now that it's here, he isn't going to squander it.

Stiles takes his time, wanting to stay true to his word and make this good for his dad. He curls his hands beneath the man's knees and pulls him down the bed so that his ass is just short of hanging off the end. This creates more space for Stiles between his legs, which he plans on taking full advantage of. Now that his dad is in a better position, Stiles runs his hands up his quivering thighs, feeling the way the fine dark hairs tickle his palms until he reaches the V of his hipbones, his eyes glued to his dad's crotch.

He wasn't kidding when he said he knew his dad was big.

Standing tall at eight inches, his daddy's cock is thick, uncut and perfectly proportioned to his large balls. Stiles spends another few moments admiring all of this before meeting the man's eyes and lowering his mouth over the head. He seals his lips around it and bobs up and down, pulling out every trick he has learned over the past three years—and he has learned a lot.

* * *

Derek very quickly becomes insensible, the pleasure of his son's tongue too much to handle. He tips his head back, breaking eye contact, and fists his hands in the sheets. He wants to buck his hips up into the wet heat but is unable to do so because Stiles still has him pinned down at his hips. His son is surprisingly strong—when did that happen?—and no matter how hard Derek tries, he can only move his hips a couple of millimetres at most. It's frustrating and amazing at the same time, the fact that someone else is in complete control of him making the blowjob even more hot. His son is a genius with his mouth, and that tongue…Derek shudders when it slides beneath his foreskin and wiggles over the glans.

Just when he is getting close to coming, Stiles pulls off. Derek raises his head to complain, but his mouth stops working when he sees his son stripping out of his own clothing.

Derek has seen Stiles naked before, of course, but it's been approximately sixteen years since he has seen him with more than his torso bared. The last time for that was a few months ago, and lot has changed even since then. Stiles has filled out quite a bit, gaining some muscle and losing the last of his baby fat. He is still smaller in stature than Derek, but the older Hale is not complaining. There's still enough there to enable Stiles to do some serious damage, which Derek wants him to.

His son's skin is pale and dotted with moles and his shoulders are broad and strong. There is a small patch of hair in the centre of his chest and a thin trail running down from his belly button, but apart from that his torso is smooth, a contrast to his dad. When Stiles pushes down his jeans and underwear, Derek sees where the treasure trail continues into a thatch of brown hair around a cock very similar to his own, like Stiles had said. It's about the same length and thickness and is also uncut, but it curves slightly upward, whereas his dad's is completely straight.

"You wanna blow me?" Stiles asks him, not failing to notice where his eyes have gone.

He is already drooling, so the answer is undeniable. Still, Derek nods and manages to croak out, "Yes."

"Good, 'cause I've wanted your cock-sucking lips around me for years."

Stiles walks around to the side of the bed, climbs on and sits back against the pillows, his legs spread invitingly. "Don't worry; I'll tell you what to do."

When his son beckons him closer, Derek turns over onto his hands and knees and crawls into the space the younger man has created for him. Up this close, Stiles' cock seems even bigger, and the scent of it fills Derek's nose, causing more saliva to build in his mouth. He snaps it shut before he can drool again and embarrass himself further, just before Stiles starts giving him instructions.

Derek wraps a hand around his son's cock and gives it a curious stroke. It feels just like his, but at the same it doesn't because he can't feel his own hand and the angle is much different.

Stiles tells him to grip his cock tighter, so he does, also increasing the speed of his strokes as he becomes more confident. After a minute of this, Stiles tells him to keep his hand gripping the base and put his mouth to work. Using his newly gained confidence, Derek flicks his tongue across Stiles' slit and swirls the taste of his pre-come around his mouth, wondering if it will be any different from his own. It probably isn't, but because it's his son's, Derek thinks it tastes better.

"Good?" Stiles asks him, his expression knowing.

"Yeah," Derek responds, going in for another taste when fresh pre-come burbles at the slit.

"Thought so. I like the taste of pre-come, too."

Soon Derek has his son's cock properly in his mouth. It feels heavy on his tongue and he gags when the head touches the back of his throat, but Stiles runs his slender fingers through his hair to soothe him and keep him from panicking. He thinks he is doing a terrible job, but Stiles still seems to be enjoying it and doesn't mind when he has to stop every now and then to catch his breath. It's surprisingly tough, and it isn't long until Derek's jaw starts to ache. He wasn't expecting it, but apparently his son was.

Stiles' hands move from his hair to cup his jaw, his fingers massaging the ache away.

"Keep going if you can," he says, maintaining control of himself a lot better than Derek had.

For a while, Derek keeps working on taking his son's cock in his throat. His eyes sting every time, but he soon manages to get an inch or two down before he has to pull off, so he figures he is making decent progress. Stiles seems to think so as well, because he grins almost proudly down at him. Such an expression makes Derek's chest feel warm.

"I knew you'd look good like this," Stiles murmurs, still massaging his dad's jaw so the ache doesn't get too bad. "Your mouth was just made for giving blowjobs."

After a few more minutes, Stiles pulls him off of his cock. "Alright, I think that's enough. Any more and I'm gonna come before I can get inside you."

"Are you doing that next?" Derek asks him, his voice gravelly because of his sore throat.

"We'll get there. I'm gonna rim you first."

Derek is on board right away. When Stiles has got out of the way, he crawls further forward so that his son can fit on the bed behind him. He is ready.

* * *

"Damn…just as amazing as I remembered," Stiles says, in awe of his daddy's ass.

It's muscular and hairy, a delightful combination. Stiles takes each cheek in hand and squeezes, approving of their firmness and the slight jiggle they still somehow have. He pulls them apart and bites his bottom lip to stop himself from moaning when he finally sees his dad's virgin asshole.

Tight and twitching from being exposed to the air, it's too good to resist.

"Get ready for me," Stiles says, all the warning he feels like giving.

"What—"

Not letting his dad get more than one word out, Stiles dives straight in. He sticks his face between Derek's cheeks and swirls his tongue around his hole, tasting him and getting it nice and wet. His dad squirms against him, like he is trying to decide whether he should try to get away from the alien sensation or embrace it. Eventually he seems to settle on the latter option, because he sticks his ass out even more so that it's easier for his son to get at his hairy little hole.

Stiles speaks right against it. "That feel good?"

"It's…weird…but I think I like it," Derek answers breathily. "Don't stop."

"Wasn't planning on it."

Stiles resumes eating out his dad, relishing the musky taste of the furled skin. Soon enough he is certain that his dad likes it. The man starts actively participating, pushing his ass back onto his face in another plea to keep going, this one silent. Stiles smirks against his dad's hole and then prods at the tight muscle with his tongue to try to get it to open up for him. It takes a while, his dad's body tightening right back up every time Stiles makes some progress, but after some persistence they get there and Stiles is able to push the tip of his tongue inside.

"Stiles!" Derek cries out, his thighs quivering with pleasure.

When he has tasted him enough, Stiles withdraws his face from his dad's ass and asks him where he keeps his lube.

"B-bedside drawer," Derek stammers, pointing toward it. "Top one."

With the half-empty tube in hand, Stiles retakes his place behind his daddy and pops the cap. "I'm gonna finger you now. Tell me to stop if you need me to and I will, okay?"

Derek inhales deeply before responding. "Okay."

Stiles uses his index finger first. He runs it in small circles around his dad's asshole, further matting down the dark hairs surrounding it, before he inserts it just up to the first knuckle. When his dad doesn't tense up too badly, he keeps pressing inside until his entire finger has been eaten up by his dad's hole. He feels the man clench experimentally around him a few times, testing the waters.

"You still good?"

"I'm good," Derek confirms, relaxing himself again.

Nodding to himself, Stiles slides his finger slowly back out, coats it in a new layer of lube and puts it back inside, not stopping partway this time. He does this several times, curling it to feel around his dad's channel. His walls are silky-smooth and burning-hot, and Stiles can't wait to feel them gripping his cock tight like a vice. He just knows it's going to be amazing.

"I'm gonna put a second finger in now. Remember to tell me to stop if you need me to."

"Yeah, yeah, I've got it. Just do it already," his dad says impatiently. Stiles can hear the eye-roll in his voice and chuckles before complying.

Despite his dad's impatience, it's a long process to go from one finger to three—and then four when Stiles slides his pinky in, just to be safe. He knows the stretch will feel like a lot for his dad. It had for him the first time he got fucked. He hadn't enjoyed it that much because in hindsight he is aware that the guy topping him hadn't done all that much to keep the experience pleasurable for both of them, only for himself.

Stiles makes sure that this isn't the case with him and his dad. With each new finger he adds he spends several minutes allowing his dad's hole to acclimate, stroking over his walls and leisurely fucking the digits in and out. He takes his time, ignoring the throbbing in his cock, and the first time he grazes his dad's prostate, Derek's reaction is explosive. He throws his head back and cries out loudly, a sound of surprise as well as pleasure.

"D-do that again!" the man demands, and who is Stiles to say no?

The twenty-two-year-old rubs the pads of his fingers across his dad's prostate every time he thrusts them forward and curls them on the way out. He spots his dad's toes curling as well.

"Stiles…please…need more."

"You sure you're ready?" Stiles asks. He doesn't want to rush and accidentally hurt him.

"I'm sure. Need you inside me yesterday."

Needing the same thing, Stiles gently removes his fingers from his dad's asshole. He gets momentarily distracted by how loose it is, how it takes a few seconds to clench up again. The fire of arousal that has been burning in his gut for nearly an hour now turns into an inferno when he glimpses his dad's pink insides, shiny and slick with lube.

"Do you have any condoms?" Stiles asks, gripping the base of his cock to stop himself from coming.

"No," Derek answers, looking back over his shoulder. "I haven't exactly needed them lately."

"You're clean, right?"

Derek nods. "Yeah, I got checked not too long ago."

"Cool. Me too. You good with going bareback?"

"I never thought I'd say this," Derek admits, his pupils dilated, "but _hell yes_."

Stiles is suddenly even more desperate to get inside his dad's ass as he was before, which he didn't think was possible. He has never fucked someone bareback before—he's a _responsible_ man-whore, thank you very much—so this should be a memorable experience for both of them. As if it wasn't already going to be.

"Should I change positions? Get on my back, maybe?" his dad enquires.

"No, this'll be the most comfortable at first. You can move when you're more used to me. Keep your back arched."

"Okay."

Stiles makes quick work of slicking up his cock. "I'm gonna start pushing in. Remember—"

"Stiles, I swear to God I'll ground you if you remind me again," Derek says sternly, shooting a challenging look back at him.

The younger man raises an eyebrow in response. "Whatever you say. Daddy."

Shuffling closer, Stiles uses his left hand to pull apart his dad's hairy cheeks and his right to guide the head of his cock to his dad's slick hole. He holds still as soon as he makes contact, the touch of his cock light like a kiss. He has broken in other guys before and in his experience they always tense up at the initial contact, even if they are actively trying not to. It's the body's natural response to something going somewhere it's not really supposed to, but he has patience and sure enough, after a few seconds of waiting, his dad's hole unclenches again and he is able to pop the head of his cock inside.

* * *

Derek's mouth hangs open when he feels the first breach. He does his best to breathe through the ensuing burning sensation, but it isn't easy. Even though he just had four of his son's fingers up his ass a minute ago, Stiles' cock already seems thicker, like it's past his limit. Several steady breaths later, though, his body relaxes enough for his son to push the next inch inside, at which point the process starts all over again.

"Breathe, dad," Stiles reminds him.

Derek is about to scold him again because he is, but then he realises that no, he actually isn't. His last breath is stuck in his lungs, and it takes work for him to expel it and refill them with new air.

Stiles running his hands up and down his back helps considerably, grounding him as more and more of Stiles' cock presses inside his no-longer-virginal asshole. When finally he feels his son's hips come to rest against his cheeks, he knows that he has managed to take all eight inches.

It was tough, and still it feels like too much, his hole clenched tight around the intrusion, but he gets himself through it by reminding himself of how much he wanted this. He wanted his son to be his first, wanted someone experienced to whom he is close, who will do their best to get him successfully through it.

"You doing okay?" Stiles asks him, his voice strained.

Derek theorises that the younger man is barely restraining himself from fucking him hard. He really appreciates it. "Give me a minute," he answers, his own cock hanging soft between his thighs.

"Sure thing."

There are a few seconds of silence, and then:

"You're doing so well," Stiles keeps speaking, his voice quiet and proud. "You already feel so good around me. Just wait: soon you'll be seeing stars and then you'll always crave a nice big cock to fuck you good. And I'll give it to you every time."

Derek's eyes widen a bit, just registering the meaning behind his son's words. "You will?"

"Oh yeah…now that I've claimed your ass, I'm not giving it up again," Stiles asserts, like there is no chance of that not coming to pass.

"Oh."

Stiles plasters himself to Derek's back and nuzzles into the side of his neck, placing delicate kisses across the sensitive skin. "You're mine now. You know that, right?"

"When did you become so…cocksure?"

"Since I went off to college and had a string of awesome flings. Turns out I'm actually a catch. Funny, huh?"

"You've always been a catch," Derek says quietly, his parental instincts kicking in. While he has his son's cock up his ass. What interesting timing.

"You're one to talk." Stiles kisses Derek's bristly cheek and then picks himself back up, his hands resting on his dad's hips. "Just tell me when I can move."

Experimentally, Derek leans forward an inch and then pushes back again, fucking himself on his son's cock. He doesn't really feel any pain anymore, just some minor discomfort which he believes he can handle, so he gives Stiles the all-clear. "You can move," he says, attempting to brace himself without tensing his body up.

"Alright."

Ever so slowly, like he is anticipating his dad taking back his permission, Stiles withdraws from Derek's ass until just the head of his cock remains inside and then pushes back in. It's an odd sensation. Derek frowns as he gets to grips with it, the feeling of something big and solid sliding in and out of his asshole, stimulating nerves within that he hadn't even known he had.

It's very different from Stiles' fingers. Derek honestly isn't sure if he likes it, but he doesn't tell Stiles to stop. He just has to give it time. His son had seemed so sure that it would feel amazing and he'd be begging for it by the end, so Derek places his faith in his son's ability to make that promise a reality.

"Doing okay?" Stiles asks him, hands stroking up and down his back once more.

"Y-yeah, I'm good," the man responds.

"It doesn't hurt anymore, right?"

"No. It's…weird, though."

"You'll get used to it."

Derek accepts this answer and bends his back a bit more to make the position easier to maintain. Doing this must change something, because the next time Stiles pushes inside, his cock glances hard off of Derek's prostate and makes him shout, surprised.

"Ah, there it is," Stiles says behind him. Derek can hear the smirk in his voice.

Every time the younger man fucks back inside now, he manages to angle his cock just right, so that he keeps hitting Derek's prostate. Soon enough, Derek can feel himself beginning to get into it, his cock hardening again between his legs as the strangeness of being fucked—the way the constant prostate stimulation makes him feel like he has to piss and the uncomfortable vulnerability it causes—is overshadowed by the pleasure of it.

His son wasn't lying when he said he was good at this. Derek can definitely believe it, and shockingly he finds himself feeling jealous when he thinks of all the other boys Stiles had broken in before him. Possessiveness surges through him, and when he remembers what Stiles had said a few minutes ago about his ass belonging to him now, he is glad.

He never wants this to end.

 _This_ is what he was missing with his ex-wife. He knows that for sure now. _This_ is where he was meant to be—getting fucked by a nice big cock, just as his son said.

* * *

When he is able to slide his cock in and out of his dad's ass without any trouble, Stiles thinks it's time to switch positions. He wants to see his dad, take in and touch his gorgeous body and watch his face as he comes apart beneath him. He fucks in one last time before pulling out completely, much to his dad's confusion.

"Why'd you stop?" the man asks him, clearly having been enjoying himself.

"Because I want you to turn over," Stiles answers.

It seems to take a few moments for his dad to get his body to cooperate, but then he flips himself over so that he is lying on his back and they can look at each other freely, without him straining his neck to look back over his shoulder. Stiles is greedy as he drinks in the state of his dad. He is flushed and a sheen of sweat covers most of his body, a wonderful sight that makes Stiles desperate to get back inside of him already and make him sweat even more. He manages to resist for now and makes use of the brief intermission he has given them.

He is mesmerised by how dad's broad hairy chest rises and falls with each breath. His nipples are still hard and slightly redder than usual, only partially recovered from when Stiles played with them earlier. The younger man runs his hand over the curves and dips of his dad's abs, feeling the way they twitch and contract at the touch before relaxing again.

He continues down the trail of hair from his dad's bellybutton and tugs lightly on his coarse pubes, admiring how the dark hairs contrast with the lightness of his dad's skin. It's like that everywhere. It's one of the things that Stiles has always loved most when looking surreptitiously at the man, the contrast of light and dark, especially how his strong jaw is framed by his dark beard.

"God, you're hot. No one else even compares," Stiles compliments, running his eyes back up the long length of his dad's body just in time to see the floridness of his face get even more pronounced, blushing cutely in a way that someone as big and strong as him shouldn't be able to do.

"Stiles…" Derek whispers, spreading his legs wider in an open invitation.

"Wow, you're already begging for it, aren't you?" Stiles chuckles fondly. "Okay then, daddy, I'll give you what you want."

Taking the invitation, Stiles fits himself between his dad's legs and hitches them around his hips. "You think you can take it a bit harder now?" he asks, ever careful despite his own desires.

Derek nods rapidly. "Just give it to me."

With a grin, Stiles guides his cock back to his dad's entrance. "Get ready then. I'm gonna give you the ride of your life."

The grip of his dad's ass seems even stronger than it was when Stiles left it a couple of minutes ago, most likely due to the change in position. He keeps things gentle for now as he once again makes room for himself in his dad's body and moves his dad's legs from around his hips to stick straight up in the air, his feet on either side of Stiles' head. His dad groans as he is filled up again, his eyes fluttering shut as he throws his head back, exposing the line of his neck. He is the most erotic sight that Stiles has ever seen, better than all the porn he has watched—which is a lot—and all the people he has fucked in the past combined. Yeah, there's no way he is giving this up for anything.

"I'm gonna go harder now," he says.

"Do it," his dad pleads, tangling his left hand in the sheets and flinging his other arm above his head.

Stiles pulls out and then with each thrust he gradually increases the power behind them. He doesn't quite go all-out because this is still his dad's first time bottoming, but the speed at which he moves appears to be enough to satisfy, judging by how hard his dad has to bite his bottom lip to keep in the noises that almost slip out. Stiles doesn't approve of this, though.

"Let me hear you," he orders, his tone brooking no argument.

Derek cracks open his eyes and stares up at him as he releases his abused and swollen lip. He looks unsure of himself when a particularly well-aimed thrust causes him to whimper, but Stiles just smiles at him, pleased.

"Stop thinking about it," he says softly, leaning down and planting a short kiss on his dad's lips. His dad's calves slip from his shoulders and his knees hook around his elbows, the position basically bending the man in half.

"It's embarrassing," Derek whispers, removing his hand from the sheets to grasp his son's arm instead.

"It's not. It's sexy as hell. I wanna hear every little noise I can get you to make."

Even though he still looks unsure, Derek gives in and Stiles picks up the pace of his thrusts a bit more as a reward. The new speed means that the sounds his dad makes get louder and more frequent, so it's a way of giving them both what they want. With that settled, Stiles unhooks his dad's legs from his elbows and presses one hand into the sheets by his dad's head, but he fully extends his arm so that he can keep looking as well as feel and hear. He uses his free hand to touch his dad, running his fingers through his soft chest hair and twisting his nipples like before, renewing their abused quality.

His dad cries out as the spark of pain heightens the pleasure coursing through him, his voice a higher pitch that usual.

Stiles is entranced. He doesn't want to blink in case he misses something.

After years of pining and taking other people to bed in hopes of forgetting about his crush on his dad, he finally has him right where he has always wanted him—writhing beneath him, lost in how good it feels to be fucked by his son's thick cock.

Up this close, the scent of his dad is all Stiles can smell, and it's heavenly. He can smell his aftershave and his sweat, and when he concentrates more on it he detects his dad's deodorant as well. He traces the latter scent back to its source and releases his dad's nipple so that he can scratch his nails through the tuft of hair at his armpit. It's slightly damp, and after a few seconds Stiles holds his fingers up to his nose to sniff them, curious.

Right away he knows that he loves it, so he angles himself diagonally and shoves his face right into his dad's armpit to get even more of that smell. The man makes a startled sound but quickly gets over his surprise and doesn't lower his arm, which makes Stiles happy. He rubs his face in his dad's damp pit and breathes him in, flicking out his tongue to taste his sweat as well as smell it. It's delectable, salty, even with the slight chemical quality it has due to the deodorant his dad put on that morning.

When his lungs start to protest, Stiles reluctantly lifts his face again.

"Stiles…" his dad whines, wrapping his legs tighter around his son's waist, pulling him in harder.

"Yeah, daddy?" the younger man questions.

"Harder. Please…need it."

It would take someone much stronger than Stiles to deny such a nice request.

He plants both hands flat on either side of his dad's head and does what he hadn't planned on doing, picking up the pace of his thrusts until their skin smacks together and he is fucking him as hard as he can. His dad is a big man, though, can take it. He stares down into his half-open hazel eyes and doesn't let up, not even when he feels his dad's nails digging into his back, scratching, leaving red trails that will last for days. Good, Stiles thinks. He wants the evidence of this encounter to last as long as it can, to have as many reminders as possible that it was real.

"I'm getting close," Derek chokes out after another few minutes, reaching between their bodies to presumably bring himself off the rest of the way.

Stiles wants to do that. He bats his dad's hand away and starts stroking his cock himself. He is amazed by how wet with pre-come it is. "Gonna come for me, daddy?" he teases. "Cover yourself in your own load?"

"Y-yeah…"

"Do it. Wanna see. Wanna feel you clamp tight around me."

His dad obeys. His body arches off of the bed as his cock spurts and he paints his hairy torso with his own seed. His ass gets impossibly tight around Stiles, so tight that it's difficult to move, but Stiles only needs a few more thrusts before he is coming as well, the sight of his dad climaxing making it too hard to hold off any longer.

Stiles buries himself to the hilt one last time and then stays there, grinding his hips in tiny circles against his dad's cheeks as his orgasm overwhelms him and he shoots deep up in his dad's guts, claiming him from the inside. He ends up collapsing on top of him, suddenly exhausted, his face tucked into his neck. He can feel the scrape of the man's beard against his forehead but he doesn't care, just keeps lying there and breathes in his familiar scent as his cock slowly softens in the grip of his dad's ass, his come already starting to seep out.

When he is able to move again, Stiles pulls out and rolls sideways, coming to lie next to his dad instead of on top of him.

"So, what's the verdict?" he asks, leaning on his elbow.

Derek smiles, his eyes still closed. "That was amazing," he says, wiggling his hips. "Feels a bit gross now, though."

"Yeah, that happens. We can shower in a minute if you want."

"Sure."

For the moment, Stiles is more than content to keep looking at the debauched state of his dad, how he is covered in sweat and his own come. He's beautiful.

After ten minutes of just lying there in silence, Stiles and his dad reluctantly get up and enter the en suite bathroom to wash the sex from their aching bodies. On the way there, Stiles gets a real kick out of how the older man has that awkward, freshly fucked walk.

"Oh shut up," Derek says, rolling his eyes when he notices the shit-eating grin on his son's face. "It's your fault."

They make quick work of showering, soaping up each other's bodies and caressing naked skin. It's loving and entirely non-sexual—one could believe it was platonic were it not for what they just did—and when the last of the soap has eddied down the shower drain, they dry themselves off with fluffy white towels, swiftly and efficiently change the bedsheets for fresh ones and then fall together onto the bed, both ready for a nap.

"Come here," Derek says, turning his back to his son.

"You like to be the little spoon, huh?" Stiles observes, covering them both with the new sheets before gladly taking up his position as the big spoon.

"I guess I do. It feels…nice."

Stiles hums contemplatively. "Y'know, I've barely unpacked anything since I moved back here."

"What's your point?" Derek asks, tugging his son's arm tighter around his middle.

"What if I unpacked in here? And what if I kept sleeping in here, too?"

His dad goes quiet, and Stiles fears that, now that the heat of the moment has passed, he will deny him. After all, he hadn't actually agreed when Stiles said his ass belonged to him now. But Stiles needn't have worried.

"I'd like that," Derek says eventually. "I'm still your dad, though."

"And you always will be," Stiles agrees. "But I still want more with you. I want everything."

The older man sighs. "Part of me hates it, but…I do, too."

"Good." Stiles presses his lips to the nape of his dad's neck. "I love you, dad. Even more now that you're a slutty bottom. _My_ slutty bottom."

Derek chuckles. "I love you, too."

**Author's Note:**

> Well, I hope you all liked my first foray into writing bottom!Derek. You have [Mulder200](https://archiveofourown.org/users/Mulder200/gifts) to thank/blame for this…and for the fact that I have now officially started to really like the idea of Derek bottoming, whereas before I was staunchly against it. You should expect to see much more of it in upcoming instalments of this kinky little series. Happy days! :P If anyone has suggestions for other PWPs they would like to see me tackle, even if you've had a prompt filled by me before, feel free to leave them in a comment down below and, if I like them, I'll try to make them happen. You can suggest _anything_ , as long as it's Sterek M/M.
> 
> In my next PWP, Stiles starts dating Derek and gets a surprise when he discovers that Derek is already in a relationship with his dog, a huge English Mastiff. Three-way bestiality ensues. If that doesn't sound like your thing, feel free to skip it. :)
> 
> **P.S. Don't forget to subscribe to me to be notified when my future fics go live, which will all be Sterek. And please check out my past fics if you haven't already and are interested.**


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